1. Field of the Invention
The invention relates to viscous, low emission fuels, including those used to power marine engines.
2. Summary of the Related Art
Large ships, such as oil tankers, cruise ships and container vessels, have historically had slow-speed engines designed to burn cheap, highly viscous “bunker fuels”; the bottom of the barrel from the petroleum distillation process. This has been economically driven, because fuel costs are estimated to amount to 35-65% of the operating costs of these large ships. As these ships approach populated areas, the combustion of bunker fuels causes harmful levels of particulate matter, nitrogen oxides and sulfur dioxide emissions that can travel inland causing severe respiratory illnesses.
In 2010, the Marine Environment Protection Committee of the International Maritime Organization (IMO) adopted detailed and stringent emissions rules for these so-called Sulfur Emission Control Areas (SECAs). Presently, SECAs include most of the coastal areas of the United States, Canada and Europe and are likely to expand. Enforcement of these SECA standards as well as proposed IMO global emission limits on new engine builds are expected to reduce sulfur emissions by 98%, particulate matter by 85% and nitrogen oxides by 80%. New sulfur standards will phase in beginning in 2012, and will reach a limit of 1,000 parts per million by 2015. In addition, beginning in 2016, newly constructed ships will be required to demonstrate advanced emission control technology in accordance to the IMO regulations.
There is, however, an enormous existing international fleet of vessels having engines that are not readily compatible with burning less viscous, lower emission fuels. These ships are expected to have serviceable lifetimes extending many additional decades until newer, cleaner fleets gradually replace them.
Approaches to lowering emissions from these large ship engines are complex and accomplish only partial emissions reductions. For example, spraying water into the fuel/air mixture during combustion reduces NOx emissions, but does not address the SOx emissions and lowers peak engine load. Another example is fuel switching to cleaner, low-sulfur diesel fuels when transiting the SECAs. This approach greatly reduces particulate matter and SOx emissions, but requires the ships to carry multiple fuel sources and does not address NOx emissions. Further, this approach presents a danger of fire and explosion when these less viscous, lower flash point fuels are used in traditional marine engine types.
There is, therefore, a need for new cleaner burning fuels having suitable viscosity and flash points for these existing engines that, once burned, offer satisfactory emission profiles. One possibility is to mix viscous chemicals having inherent heat content with cleaner fuel oils. However, such chemicals tend to phase separate from the fuel oil, requiring mixing immediately before combustion, which is inconvenient and can be dangerous if done improperly. The present invention addresses these difficult problems.